In one embodiment, an optical fiber includes an inner core having a core refractive index delta and profile shape parameter α in the range of 1.8 to 2.6, including endpoints, and a cladding layer surrounding the inner core. The cladding layer includes an inner cladding segment having an inner refractive index delta, a trench segment having a trench refractive index delta, and an outer cladding segment having an outer refractive index delta. The optical fiber further includes a coating layer surrounding the cladding layer and having a thickness of less than 30 .Math.m and a modulus greater than or equal to 0.5 GPa.

Optical transmission systems and methods are disclosed that utilize a QSM optical fiber with a large effective area and that supports only two modes, namely the fundamental mode and one higher-order mode. The optical transmission system includes a transmitter and a receiver optically coupled by an optical fiber link that includes at least one section of the QSM optical fiber. Transmission over optical fiber link gives rise to MPI, which is mitigated using a digital signal processor. The QSM optical fiber is designed to have an amount of DMA that allows for the digital signal processor to have reduced complexity as reflected by a reduced number of filter taps as compared to if the DMA were zero.

The MCF of the present disclosure suppresses XT and leakage loss at 1.565 μm or 1.625 μm for bidirectional communication. The MCF comprises 12 core units each including a core and a depressed layer, a common cladding, and a resin coating. The units are arranged so that no adjacent relationship is established between cores each having an adjacent relationship with a specific core selected from the units, and are arranged so that centers of the units are line symmetric with a symmetry axis intersecting with the central axis and passing through none of the centers of the units. The resin coating's diameter is 250±15 μm, an effective area at 1.550 μm is 70 μm.sup.2 or more, and a 22 m-length cable cutoff wavelength is 1.530 μm or less. A center-to-center interval between adjacent cores, a shortest distance from the core center to the cladding interface, and a cladding's diameter satisfy specific conditions.

A single mode optical fiber is provided that includes a core region having an outer radius r.sub.1 and a maximum relative refractive index Δ.sub.1max. The single mode optical fiber further includes a cladding region surrounding the core region, the cladding region includes a depressed-index cladding region, a relative refractive index Δ.sub.3 of the depressed-index cladding region increasing with increased radial position. The single mode optical fiber has a bend loss at 1550 nm for a 15 mm diameter mandrel of less than about 0.75 dB/turn, a bend loss at 1550 nm for a 20 mm diameter mandrel of less than about 0.2 dB/turn, and a bend loss at 1550 nm for a 30 mm diameter mandrel of less than 0.005 dB/turn. Additionally, the single mode optical fiber has a mode field diameter of 9.0 microns or greater at 1310 nm wavelength.

An optical fiber includes a core and a cladding surrounding an outer periphery of the core and has a refractive index profile in which a relative refractive index difference with respect to a distance r from a center of the core is represented by Δ(r), where a value of A represented by

A=−∫.sub.0.sup.0.22MFD.sup.1.31(Δ(r)−Δ.sub.ref(r))dr+∫.sub.0.22MFD.sub.1.31.sup.0.44MFD.sup.1.31(Δ(r)−Δ.sub.ref(r))dr  (Formula 1)

is 0.3%.Math.μm or less, where a unit of r is μm, a unit of a relative refractive index difference Δ(r) is %, Δ.sub.ref(r)=−0.064r+0.494, and MFD.sub.1.31 is a mode field diameter at a wavelength of 1.31 μm.

In an optical fiber, a plurality of individual cores extend through a common cladding. Each individual core supports at least one local transverse spatial mode. The individual cores and surrounding cladding are structured to support propagation of plurality of desired signal-carrying modes, while suppressing undesired modes, thereby supporting the propagation of one or more spatially multiplexed signals. The core-to-core spacing of the fiber is configured to maintain an acceptably low level of mode-coupling between cores.

An optical fiber includes a core region of silica glass doped with an alkali metal oxide. A depressed-index cladding region surrounds the core region and comprises silica glass doped with a first concentration of fluorine. The depressed-index cladding region has a minimum relative refractive index Δ.sub.3min in a range from −0.80% to −0.30%. An outer cladding region comprises silica glass doped with a second, lesser concentration. The outer cladding region has a relative refractive index Δ.sub.4, where Δ.sub.4−Δ.sub.3min>0.05%. The optical fiber has a time-to-peak hydrogen aging value at 23° C. of less than 100 hours upon exposure to an atmosphere having a total pressure of 1 atm and containing a partial pressure of 0.01 atm H.sub.2 and a partial pressure of 0.99 atm N.sub.2. The optical fiber exhibits an attenuation <0.16 dB/km.

A rollable optical fiber ribbon utilizing low attenuation, bend insensitive fibers and cables incorporating such rollable ribbons are provided. The optical fibers are supported by a ribbon body, and the ribbon body is formed from a flexible material such that the optical fibers are reversibly movable from an unrolled position to a rolled position. The optical fibers have a large mode filed diameter, such as ≥9 microns at 1310 nm facilitating low attenuation splicing/connectorization. The optical fibers are also highly bend insensitive, such as having a macrobend loss of ≤0.5 dB/turn at 1550 nm for a mandrel diameter of 15 mm.

A multimode coupling fiber for optical data links features low coupling loss to silicon photonics lasers, VCSELs, single mode transmission fibers, multimode transmission fibers, and high speed receivers. The coupling fiber includes a core, an optional inner cladding region, a depressed index cladding region, and an outer cladding region. The relative refractive index profile of the coupling fiber includes a core region with α profile and a depressed index cladding region that facilitates low bending loss and high bandwidth. The mode field diameter of the coupling fiber is well-matched to standard single mode transmission fibers and the etendue of the coupling fiber is high enough to couple efficiently to multimode transmission fibers.

An embodiment of the invention relates to a GI-MMF with a structure for achieving widening of bandwidth in a wider wavelength range and improving manufacturing easiness of a refractive index profile in a core. In an example of the GI-MMF, a whole region of the core is doped with Ge and a part of the core is doped with P. Namely, the Ge-doped region coincides with the whole region of the core and the Ge-doped region is comprised of a partially P-doped region doped with Ge and P; and a P-undoped region doped with Ge but not intentionally doped with P.